The present invention relates generally to a processing method, and more particularly to a processing method that transfers a pattern of an original onto a resist applied substrate. The present invention is suitable, for example, for a processing method that utilizes photo-curing type nanoimprint lithography for fine processing used to manufacture Micro Electro-Mechanical Systems (“MEMS”), photonic crystal, and an optical element.
Nanoimprint is one known alternative technology to a fine pattern forming method for a semiconductor device that utilizes the photolithography with the ultraviolet (“UV”), X-ray, and an electron beam. The nanoimprint is a technology that presses an original (also referred to as a “mold” or a “template”) on which a fine pattern is formed by the electron-beam lithography etc., against a substrate such as a wafer to which a resinous material (resist) is applied, thereby transferring the pattern onto the resist.
A photo-curing method is proposed as conventional nanoimprint lithography. See, for example, U.S. Pat. No. 6,334,960. The photo-curing method is a method of exposing the UV-curing resin as the resist while pressing a transparent mold against the resist, and of releasing the mold after the resin is cured.
Other prior art include Japanese Patent Applications, Publication Nos. 11-074190, 10-312957, and 2000-137319.
However, the conventional photo-curing method cannot maintain the intended pattern transferring precision. In general, in the photo-curing method, the original is made of UV-transparent quartz, which is a highly rigid material. It is known that the UV-curing resin causes volume shrinkage, for example, by about 7% to about 10% in the UV curing course from liquid to solid. On the other hand, the original is made of a highly rigid material, and the volume shrinkage is negligible. The instant inventors have discovered that when the UV light is irradiated while the original is pressed against the UV-curing resin, a volume shrinkage factor of the UV-curing resin differs according to locations due to the rigidity of the original, the surface tension of the UV-curing resin, and the uneven surface free energy (interfacial tension) of the original. In other words, a simply entirely enlargement of the original's pattern by about 7% to about 10% does not result in a desired pattern since the shrinkage factor differs according to locations or since the shrinkage is distorted.
The wafer size varies in the semiconductor device manufacture after undergoing various processes, such as a heat treatment. Therefore, as disclosed in Japanese Patent Applications, Publication Nos. 11-074190, 10-312957, and 2000-137319, in pattern transferring, a correction in accordance with the wafer's magnification is needed for the original by means of the temperature and the load. This correction is often referred to as a “magnification correction.” Different from the volume shrinkage, the magnification correction is a uniform correction for the entire original or substrate. However, since the original is highly rigid, a magnification correction needs a heavy load and a great temperature change, causing a deformation of the original and a deteriorated pattern transferring precision. In addition, use of wide-range load or temperature control mechanism would make the apparatus structurally complicated, increase its size and the cost, and lower the throughput.